Tea has long been considered a tonic for health with both black and green teas being studied for their health-giving properties. Tea contains many bioactive plant chemicals known as polyphenols (tea polyphenols are sometimes termed catechins) which can act as antioxidants in the body and thus potentially be important for disease prevention.
A recent study has shown (1) that green tea may have an effect on the risk factors for heart disease via improving the function of cells, called epithelial cells, which line the circulatory system. When these cells are not functioning properly it can lead to the progression of atherosclerosis. Atherosclerosis is commonly described as ‘hardening of the arteries’ it is a chronic inflammatory response in the walls of arteries
The study was small and preliminary but found that green tea consumption has an acute beneficial effect on endothelial function in a large artery (brachial artery) in healthy individuals (when compared to caffeine or hot water). Green tea seems to work by improving blood flow and the ability of arteries to relax. The effects were evident fairly rapidly, almost immediately in fact, within 30 minutes of drinking the tea dilation (relaxing) of the artery could be detected. Measurement of the arteries was performed by high resolution ultrasound. The researchers only looked at short-term impact (up to two hours). It is not yet known what the long-term benefits could be. Further studies are being carried out
Previous studies have found that black tea has also been associated with improved endothelial performance but adding milk to black tea may well reduce the health benefits associated with tea drinking. Green tea originated in China but is now a popular drink that is consumed throughout the world. Both green and black tea come from the same camellia sinesis bush but the different processing technique create the differences between the teas. Green tea is not fermented whereas black tea is, the fermentation process is the reason for the brown/dark colour and the different flavour of black tea. The flavonoids in green tea are probably more potent antioxidants than those found in black tea due to the different processing techniques.
A cup of tea isn’t going to cure or prevent illness and disease as a stand alone addition to normal daily life! A healthy lifestyle is one that includes healthy eating, physical activity and other lifestyle factors. Including green tea can be seen as a way to boost antioxidant defences in conjunction with a healthy lifestyle. Green tea supplements which contain high doses of the tea polyphenols (e.g. catechins) are now widely available to buy but as yet it is unknown if the potential benefits extend to the supplemental form of the flavonoids.
(1)Alexopoulos N et al. 2008. The acute effect of green tea consumption on endothelial function in healthy individuals. Eur J Cardiovasc Prev Rehabil. 15:300-305
Written by Ani Kowal